FIG. 1 shows a schematic representation of a contemporary cellular network 1. The architecture of these cellular networks comprises a network subsystem 2, a base station subsystem 3 and a mobile station 4. Examples of these cellular networks are GSM and DCS and extensions of these networks such as GPRS, UMTS etc. The network subsystems main component involves the mobile switching centre 20 (MSC) providing the interface of the cellular network and wire-bound networks 5 (PSTN, ISDN, ADSL etc.) as well as roaming and call-routing facilities (Home Location Register 21, Visitor Location Register 22, Equipment Identity Register 23 and Authentication Centre 24).
The base station subsystem 3 consists of a number of base stations. The base station subsystem 3 constitutes the connection between a mobile station 4 and the MSC 20. The base station subsystem 3 may be distinguished into two parts, the Base Transceiver Station 31 (BTS) and the Base Station Controller 30 (BSC). The BTS 31 houses radio transceivers that define a cell and handles the radio-link protocols with the mobile station 4. In a large urban area, there will potentially be a large number of BTSs deployed. The BSC 30 manages the radio resources for one or more BTSs 31. It handles radio-channel set-up, frequency hopping, and handovers.
The mobile station 4 is the mobile equipment that enables a user to communicate with others through the cellular network. A mobile station 4 usually comprises mobile equipment 41 and a Subscriber Identity Module 42 (SIM).
As the complexity of cellular networks increases, flexible operation of these networks becomes more difficult. Configuration and reconfiguration of a cellular network is complex since the parameter settings of the different components of the cellular radio network affect each other. U.S. Pat. No. 5,434,798 of Ericsson describes a reconfiguration method and apparatus in which the cell parameters of particular mobile switching centres in a network are copied to a database, and the copied parameters are stored. A set of proposed changes to the stored parameters is prepared and the consistency of the prepared set of proposed changes is verified. Alterations to the set of proposed changes responsive to the verification are made and the verified set of proposed changes is copied to the concerned mobile switching centres. The verified set of proposed changes is then introduced into the network. An up-to-date image of the cell parameters in the mobile switching centres in the network is maintained in a system parameter database.
Problem Definition and Aims of the Invention
Typically, a cellular radio network comprises several MSCs and a larger number of base stations. Operation of such cellular radio networks requires a high degree of flexibility in the sense that configuration and reconfiguration of the cellular network has to be possible within a limited period of time and with a high degree of accuracy. Such a reconfiguration of a radio network can be permanent or temporary. Reasons for such a reconfiguration are numerous, e.g. a temporary cell split needed to deal with an expected increase in traffic due to an event or the permanent integration of new elements both affecting the settings of already existing elements in the radio network. Therefore, sophisticated methods and systems are required that administer the parameter settings of the various components, e.g. the BTS or BSC, of the cellular radio network and change the parameter settings of those components. Examples of parameters that can be changed include cell type, cell designation, cell direction, signal strength, signal to noise ratio, etc. Moreover, means have to be provided in order to check the consistency of the proposed parameter changes before the changes are implemented in the cellular network.
The reconfiguration method and system as revealed by the '798 patent can be improved with regard to, inter alia, the performed routine to check the consistency of proposed parameter changes.
More particularly, an improvement relates to the hierarchical levels that can be checked. The method of the '798 patent checks the consistency of the proposed parameters only with regard to cells and handovers. Thus, only a very limited part of the network hierarchy is checked, resulting in a less reliable and efficient control of the radio network.
Another problem of the method described in the '798 patent relates to the type of rules used in performing the consistency check. The rules used in performing this check originate solely from technical requirements derived from cellular network technology. There is no possibility to apply rules derived from operational practice as well. Moreover, it is not possible to deviate from the technically sufficient parameter setting requirements if operational practice experience reveals a different more preferable technical parameter setting.
Still another problem of the method described in the '798 patent is that, in performing the consistency check, only pre-programmed rules are used. This limitation decreases the flexibility of the system for the operator that exploits a cellular radio network. It may be that such an operator is not satisfied with the requirements for the various parameters defined by the supplier of the network. The operator may want to define the requirements, including the technical requirements, himself.
The present invention aims to provide a method and system to check the consistency of the proposed changes of parameters.